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Headlight maintenance: Keep your lights in tip-top shape


Driving in the dark or in harsh weather can be difficult. Maintaining your headlights will help ease the stress of driving in these conditions. 

car with headlights

Keeping your headlights in good working order is a legal requirement.

And, being caught with your fog lamps on unnecessarily could lead to a fine or points on your licence. 

However, simple checks can be performed to maintain your headlights and keep you safe on the road. 

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Simple headlight maintenance tips

Headlights should be a part of your regular maintenance checks. Here are some things to look out for:

  • Always make sure your headlight casings are clean.

  • Check brake lights and indicators. This is easily checked by getting a friend to look around the vehicle while you’re inside working the controls.

  • Be aware, you may not notice a blown headlight. Usually you’ll notice a reduction in brightness first or other road users will flash their lights at you.

  • If your indicating bulb is blinking faster than it should, it could mean it’s not working correctly. 

  • If you're replacing bulbs, always do so in pairs. There’s a good chance the other one won’t be far behind.  

If you’re in doubt, pop to your local garage for advice. 

Dashboard signals and their meaning 

Symbol Type of light Description
full beam
Full beam Usually a blue coloured symbol on the dashboard.
Dipped beam Dipped beam This is the symbol you should see if you’re on a highway at night and encountering traffic.
front fog light
Front fog lights These should be used when you cannot see for more than 100 metres (328 feet) in front of you. Once visibility improves, they should be switched off.
rear fog light
Rear fog lights These should be used when you cannot see for more than 100 metres (328 feet) in front of you. Again, they should be switched off when visibility improves.
self leveling headlights Self-levelling system When a car behind you goes over a speed bump, the light can catch in your rear view mirror, briefly dazzling you. Self-levelling headlights stop this as they keep the lights aimed at the road.
brake light warning
Brake light warning If there’s an issue with your brake light this symbol will usually appear.
bulb fault Exterior light/bulb fault This symbol will appear if there’s an issue with your exterior headlights. Either a bulb malfunction or an electrical issue.
parking lights Parking lights The small lights on the side of the vehicle used for parking at night.

Other dashboard symbols can signify faults or checks that need to take place. Always keep an eye on them.   

Headlight laws

Law defines night as the hours between half an hour after sunset and half an hour before sunrise. Within these times your headlights should be switched on. 

There are strict rules on headlights which state:

Sidelights and rear registration plate lights should be lit between sunset and sunrise. Except on a road lit with street lighting.These roads will usually have a 30 mph speed limit.

Conversely, you shouldn’t use any lights in a way which would dazzle or cause discomfort to other road users. This includes pedestrians, cyclists and horse riders.

You must also use headlights when visibility is reduced. For example when you can’t see more than 100 metres (328 feet) in front of you.

You may also use your front or rear fog lights but you must switch them off when visibility improves.  

In stationary queues of traffic the parking brake should be applied. Your foot can then be removed from the footbrake. This will deactivate the brake light and minimise glare for other road users.

headlight controls

Headlight technology

Xenon HID technology

If you’ve been driving along a highway and noticed a slightly blue tinge to another drivers headlights, the chances are they’re HID bulbs. 

HID bulbs have no filament which can be prone to vibration. Instead they’re filled with xenon gas and contain two electrodes (one on each end of the bulb). 

When the bulb is switched on an electric current passes between the two electrodes and the xenon gas lights up. 

This is only used during start up, once the desired temperature inside the lamp is reached, other gases ensure it stays lit. 

The benefits of Xenon HID bulbs is the increase in brightness. They also use much less energy to produce this light, making them an efficient option for drivers. 


This stands for light-emitting diode. It uses a semiconductor diode, which glows when voltage is applied. 

Again, the upside of these is that they’re very bright, and they use far less energy than halogen bulbs. You also can avoid periodic bulb blows, as LEDs can last for more than 20 years. 

The brightness of these bulbs is also far better than halogen lamps. They’re also slightly superior to xenon-HID bulbs, as they tend not to dazzle other road users. 

Always use a reputable seller if you’re interested in LED lights. Cheap LEDs can often be too bright, and cause discomfort to other road users.

You must also ensure that they’re properly aligned so they’re not shining directly in the eyes of other road users.

First published 19 December 2017.


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